Elastic fluid mechanism



R. BIRMANN ELAsTIc FLUID MECHANISM Sept. 10, 1946.

Filed May 2, 1942 gru. Z

Patented Sept. 10, V1946 j' mesne assignments, to Federal Reserve Bank of f Philadelphia, acorporation of the UnitedStates of America Application May 2, 1942, serial No. 441,538

9 Claims; (01.,60-49) This invention relates to elastic fluid mecha--` nisms, andv more particularly to the construction ofgturbine blading, to provide eiective cooling thereof. y y

In my Patent Number 2,283,176, dated May 19,`

1942, there are disclosed methods and means for cooling elastic fluid turbines, particularly of the types operating at very high temperatures through the use of products of combustion as driving uid, thisr cooling being effected with at least no substantial loss of energy by imparting heat energy to the cooling, gases and then vrecovering a substantial part of such energy as either pressure of the exhausted gas or rotational effort on the turbine wheel. In the Vpreferred mode of utilization ofthel invention of said prior application,the` turbine gas passages andthe cooling gas passages are separate and alternate about the turbine wheel. The cooling gas passages, which in practice generally handle air, are provided with impellel` intake portions adapted tov turn the gasI flow radially outwardly, and thereby effect substantial compression. This por-` tion of vthepassageis thenfollowed by a portion designed similarly to a turbine bucket from which the gas is discharged rearwardly with respect to thedirection of rotation. During the compression in the impeller portion of the cooling gas passage, the transfer of heat to the gas is desirably at a minimum, though necessarily f.

some transfer occurs from the walls of the passage. A major portion of the heat transfer oc.- eurs', however, near the completion of the compression and rthrough the portion of the passage joining the impeller and thev turbine portionsA and l.

same field. While, where a maximum degree-of strength is required, the arrangements of 4said prior applications are preferable, the present invention may be utilized where there. is a permissible sacrice of strength, i. e., where the-operar, tion is not at extremely high speeds or where more moderate temperatures are encountered.I i

The above general object of the invention, as Well' as other objects relating to detailsrwillbe made apparent from the following description, read in conjunction with the accompanying drawing, in which: 1 1 Y Figure l is a diagrammatic sectionalfview il-v lustrating a portion of a turbine `wheel oo nst-ructedv in accordance with the present invention, the View showing a circumferential projection of a section taken on a surface throughy the center` of a blade;

Figure 2 is a section taken onthe cated at 2-2 in Figure 1; Figure 3V is a. section taken onv the plane indie cated at 3 3 in Figure 1; and 1 Figure 4 is a section taken on the plane indicated at 4--4 in Figure 1. Y

The hub 4of the turbine wheel embodyinggthe invention is indicated at 2 and carriesblades of, the general type described inv detail in said application Serial No. 422,837; i. e., each of the blades may be considered as formed on a doubly ruled surface dened by the equation x=K tan b, in which b is measured about the axis of rotation and :l: is measured along said axis. As will be plane indievident from my Patents 1,926,225dated; Sepin the latter portion. vThe expansionof the cornpressed and heated gas causes the transformation of both the pressurel and heat energy to a substantial extent into kinetic energy of the gas which is discharged in the form of a high velocity jet relative to the turbine wheel. This working torque is applied tothewh'eel, aiding the mainY driving gases in.' effecting rotation of, the shaft to carry the load.

The broad object of the present invention is the provision of an arrangement of the type described in whichmore effective heat transfer to the cooling gas may be provided while at the same time various advantages of construction result, particularly in making it possible to provide the turbineblading in simple fashion, it Lbeing diiiicult to form the cooling gas passages'as described in said Patent 2,283,176 or asV disclosed in my application Serial No."42 2,837, filed December 13, 19491,.relatingto,improvements inthe 55 radially rfrom these holes aremilled slots. 6,.,

tember 1,2, 1933,l 1,959,703, dated May 22, 1934, and 2,283,176, dated May 19,71942, 0ne setfof straight lines of any such surface'bear a skew relationship to the axis of rotation, while the other set extends radially. The lines of the formerset, in circumferentialv projection, will ap,-` pear as hyperbolas and, infact, so appear'in the projection of Figure 2. l

It will-beevident that, ldueto these properties of .the theoretical Vane or blade surface, it is possible to insert blades into drill holes in a hub havingy as axes the straight lines ofskew are rangement as just described, such setting of blades or Vanes in a hub being illustrated in said Each of the blades comprises two sections 8 and I of the type indicated in the drawing provided, respectively, with semicircular base portions I2 and I4, which, together, form a cylindrical base element receivable within Ithe drilled bores 4 with the por-tions 8 and I0 of each blade extending outwardly through the milled slot 6. A further slot of varying depth is formed in the bottom portion of each bore 4 as indicated at 8, serving, as will be pointed out hereafter, to provide for the distribution of cooling `air or other gas within the blades. The inner adjacent portions of the blade sections 8 and IIJ contain depressions which, when the sections are assembled, form a hollow cooling space. In order to provide proper spacing and rigidity, the blading sections are caused to engage each other at various points. At the inner portions of their exit ends, the blade sections are provided with padsv I6 `and I8, in which there are formed straight grooves combining to constitute an opening 28. On the inner surfaces of ,the intermediate portions of the blade sections there are formed additional pads 22 and 24 adapted to engage each other, while the outer edges of the blade sections further come in contact as indicated at 2B and 28, and their entrance ends are also closed by.

contacting portions 32. These various pads and contacting 'portions are suitably finished, and the blade sections may then be welded together wherever desired, for example at the engagements of the cylindrical base portions I2 and I4 and at 30 about their edges at 26 and 28, and at 32 to form unitary blades insertable into the bores and slots 4 and 6 previously described within which they may be secured by welding or in any other fashion.

Communicating with the slots 8 are drilled holes -34 opening forwardly in the direction of rotation of the rotor so as to receive air and act as impeller passages. The center lines of these drilled holes are straight and bear a skew relationship to .the axis of rotation, as a result of which the straight drill hole 34 appears to be hyperbolic in form in the circumferential projection of Figure l.

' The rotor is .assembled in a conventional housingindicated at 36 and into .the spaces between the blades are directed driving gases through nozzles 38 in the usual fashion.

` In the operation of the turbine wheel, the driving gases flow between `the blades in conventional fashion, being discharged rearwardly relative to the blades to the right as viewed in Figure l. At

the high speeds of rotation, the cooling air or 1 other gas is compressed in the impeller passages 34, whence it enters the groove 8 to be distributed along 4the length of a blade into its hollow portion 40 through the openings provided at 39, the space between the blade sections being open at the innermost portions thereof except in the vicinity of the pads I6 and I8. The air entering the space within each blade flows upwardly and then turns to flow through the open end of the hollow space within the blade at the discharge end of .the blade. 'Ifhe pads 22 serve in part as guide vanes to cause the ilow to reach the uppermost portions of the interior of each blade; so that adequate cooling of the entire blade area is effected. Flow through the hole aids in cooling the region about the pads I6 and I8.

The advantages of this construction may be summarized as follows:

A thin, uniform wall thickness canbe obtained in the case of each blade, 'which isa great advantage in eliminating thermal stresses, which Iarise if differences in thickness occur in blades subject to large temperature gradients.

By the adoption of this construction, the vanes can be produced from a material which cannot be machined, but which can be ground to proper finish, after being die forged or cast. This is of considerable advantage, since may of the best heat-resisting alloys lare so hard that they `cannot be formed by machining.

The cooling space in the interior of each blade can be arranged over the entire extent of the blade, an end which is almost impossible to accomplish by machining, the cooling passages in the case of machined blade constructions being from a practical standpoint restricted to a considerable extent.

The cooling space is in the form of a thin sheet, the thickness of which is much less than could be produced by machining or by any method not involving splitting the vanes in the manner illustrated. The surfaces of the cooling space, furthermore, may be smooth to such extent as to oier a minimum resistance to flow. Due to the thinness and uniformity of the cooling space, the complete vanes can be made thinner and lighter resulting in the additional advantage of leaving more space for the working gases, i. e., considerably less circumferential space is taken up by the vanes than in the case of former constructions.

The sole disadvantage of this construction is that it is not as strong as those constructions which involve the machining of blades directly from a wheel blank.V However, as pointed out heretofore, the construction may be used where extremely high stresses are not encountered.

It will be obvious that various departures may be made from the construction disclosed while retaining the advantages inherent in the invention.

What I claim and desire to protect by Letters Patent is:

1. A turbine rotor comprising a hub member containing grooves extending along straight lines bearing a skew relation to the axis of rotation, and vanes secured in said grooves and extending outwardly therefrom to dene bucket passages opening rearwardly with respect to the direction of rotation, said vanes being hollow to provide cooling gas spaces opening rearwardly, and the hub member being provided with impeller passages communicating with the spaces in said vanes and having skew directions relative to the axis to neiiect picking up of the cooling gas.

v2. A turbine rotor comprising a hub member containing grooves extending along straight lines bearing a skew relation to the axis of rotation, and vanes secured in said grooves and extending outwardly therefrom to define bucket passages opening rearwardly with respect to the direction ofrotation, each of said vanes being formed of two parts constituting a hollow structure to provide a cooling gas space opening rearwardly, and

the hub member being provided with impeller passages communicating with the spaces in said vanes and having skew directions' relative to the axis to effect picking up of the cooling gas.

3. A turbine rotor comprising a hub member containing grooves extending along straight lines bearing a skew relation to the axis of rotation, and vanes secured in said grooves and extending outwardly therefrom to define bucket' passages opening rearwardly with respect to the direction of rotation, each of said vanes being formed of two parts welded together constituting a hollow structure to provide a cooling gas space opening rearwardly, and the hub member being provided with impeller passages communicating with the spaces in said vanes and having skew directions relative to the axis to eiect picking up of the cooling gas.

4. A turbine rotor comprising a hub member containing grooves extending along straight lines bearing a skew relation to the axis of rotation,

each of the grooves comprising a cylindrical porvbearing a skew relation to the axis of rotation,

each of the grooves comprising a cylindrical portion and an outward extension therefrom, and vanes comprising cylindrical base portions fitting in the cylindrical portions of said grooves and extending outwardly through said extensions to define bucket passages opening rearwardly with Y respect to the direction of rotation, reach of said vanes being formed of two parts constituting a hollow structure to provide a cooling gas 'space opening rearwardly, and the hub member being provided with impeller passages communicating with the spaces in the vanes and having skew t directions relative to the axis to effect picking up of the cooling gas. Y

6. A turbine rotor comprising a hub member containing grooves extending along straight lines bearing a skew relation to the axis of rotation, each of the grooves comprising a cylindrical por- `in the cylindrical portions of said grooves and extending outwardly through said extensions to define bucket passages opening rearwardly with respect to ther direction of rotation, each of said vanes'being formed of two parts welded together constituting a hollow structure to provide a cooling gas space opening rearwardly, and the hub member being provided with impeller passages communicating with the spaces in the vanes and having skew directions relative to the axis to eiect picking up of the cooling gas.

7. A turbine rotor comprising a hub member, and vanes secured to the hub member and extending radially outwardly therefrom, each of said vanes being formed of two parts constituting a hollow structure to provide a cooling gas space opening rearwardly, and the hub member being provided with impeller passages communicating with the spaces in said vanes and having skew directions relative to the axis to effect picking up of the cooling gas.

8. A turbine rotor comprising a hub member, and vanes secured to the hub member and extending radially outwardly therefrom, each of said vanes being formed of two parts welded together and constituting a hollow structure to provide a cooling gas space opening rearwardly, and the hub member being provided with impeller passages communicating with the spaces RUDOLPH BIRMANN. 

